Fuel metering system



Oct. 25, 1 960 L 2,957,467

FUEL METERING SYSTEM Filed Aug. 25, 1958 INVENTOR. 720/7745 Mfidzl 2,957,467 Patented Oct. 25,- 1960 FUEL METERING SYSTEM Thomas M. Ball, Bloomfield Hills, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Aug. 25, 1958, Ser. No. 756,859 Claims. (Cl. 123-119) This invention relates to fuel metering systems for in ternal combustion engines and in particular to improvements on fuel metering systems which inlet meter fuel according to air flow to the engine. Systems of this general type are disclosed in Paten Nos. 2,414,322 and 2,447,261 to Mock.

In the aforementioned systems the formation of fuel vapor in the conduits and various chambers thereof is a serious impediment to the proper metering and distributing of liquid fuel to the engine cylinders. During engine operating conditions of light load and high tem peratures the formation of fuel ,vapor in said conduits and chambers of the system may become so great in proportion to liquid fuel as to cause erratic fuel metering and distribution resulting in poor engine performance and loss of engine power. A major portion of the fuel vapor formed in these systems results from the pressure drop across the inlet metering valves of these systems and can be only partially removed by vapor separators, traps and bleeds which are bulky, inefficient, and require additional fuel booster pumps to compensate for the fuel pressure drops thereacross.

It is an object of this invention to provide a relatively cheap and easy to construct mass flow fuel metering system overcoming the aforesaid objectionable fuel vapor formation.

Another object is to provide an air flow fuel metering system with return flow metering structure to eliminate vapor formation in said system.

Another object is to provide a fuel metering system capable of metering liquid fuel to an internal combustion engine in proportion to the air flow to said engine over the entire speed range of the engine and under high fuel vaporizing conditions.

Another object is to provide a mass flow metering system with a means to prevent excessive fuel vaporization in the system, to purge vapor from the feed fuel and to return said vapor to the fuel supply.

In carrying out this invention a fuel metering system of an internal combustion engine is provided with a constant delivery fuel source, a fuel feed conduit connecting the fuel source to the engine, and a return flow conduit connecting the fuel feed conduit to the fuel source to bypass a portion of the feed fuel back to the fuel source. In order to vary the amount of fuel flowing to the engine a return flow metering valve is provided in the return flow conduit which valve is adjustable to allow all or any part of the fuel delivered to the fuel feed conduit to be returned to the fuel source. The adjustment of the valve is accomplished by connecting air pressure responsive means to the movable portion of the valve and to air flow metering means such as venturi tubes positioned in the intake manifold conduits of the engine. As air flow or mass flow to the engine increases the pressure signals transmitted to the pressure responsive means will become stronger and the valve will consequentlybecome further closed to restrict the flow of return fuel and to thereby increase the proportion of feed fuel flowing to the engine.

To make the above fuel metering system self-adjusting and to maintain the fuel flow to the engine linear with respect to the air flow thereto a fuel jet and fuel pressure responsivev means are positioned in the fuel feed ronduit. The fuel pressure responsive means is connected to the movable portion of the return flow meteringvalve and is responsive to the fuel pressure drop across the fuel jet to adjust said valve. The venturi tubes, air pressure responsive means, fuel pressure responsive means, and fuel jet are so proportioned in size that for a given and constant air flow in the intake manifold conduits the return flow metering valve will assume a constant adjustment and the fuel flow through the jet will be linear with respect to said airflow. This linear relationship is desirable for proper engine performance.

Variations in the number of air conduits, venturi tubes, pressure responsive means, and fuel jets may be readily incorporated in the system to provide a suflicient air flow signal to obtain proper fuel flow over the entire speed range of the engine. The air flow may be regulated by the conventional manually operated throttles. These throttles located in the manifold air conduits may be linked in such a manner that air will be allowed into one conduit only at a predetermined air flow in another conduit. This delayed action operation of a throttle may be accomplished by mechanical or fluid means as shown and described below. Secondary, adjustable area fuel jets may be provided in the main fuel passage to provide for an additional flow of fuel in response to the opening of a secondary throttle.

The constant quantity of fuel supplied by the source is in excess of the maximum amount required by the engine and the excess is returned to the tank through the return flow conduit. As opposed to direct fuel inlet metering of the type shown in the aforementioned patents the throttling of the fuel takes place in the present system across the return flow valve orifice and the vapor formed due to the pressure drop thereacross is immediately carried back to the tank to bleed off from a vent therein. Moreover, at light load the major portion of the fuel supplied by the source or tank is returned through the return flow conduit and in so doing any vapor present in the feed fuel is purged therefrom before it passes through-the fuel jets to the engine or to a distribution chamber which distributes the fuel to the separate cylinders of the engine.

By so eliminating most of the vapor from the feed fuel, pressures developed by the small amount of remaining vapor do not seriously offset the valve adjusting function of the fuel pressure responsive means and the proper amount of fuel is returned to the fuel tank. Also, significant quantities of vapor are transmitted to the engine in place of liquid fuel to thereby lean the fuel-air combustion mixture.

Further objects and advantages will become apparent from the following description and drawings in which identical characters represent identical structure in the several figures and in which:

Figure 1 represents a cross sectional view of a mass flow metering system having return flow means thereon;

Figure 2 represents a variation of the system of Figure 1; and V Figure 3 represents a variation of the system of either Figures 1 or Referring to Figure l the mass flow fuel metering system is generally designated as 10 and comprises essentially primary and secondary air intake conduits 12 and 14 communicating with the engine cylinders, airflow metering means 16 and 18, fuel feed conduit 20, return flow conduit 22, and pressure responsive adjustable fuel metering means 24. Metering means 24 comprises a 'to chamber 40 feed or nozzle feed conduits fuel to tank 50 along with any 'ing projection 68 slidably rides.

- it is assumed ,normal idling positions.

force developing air flow section 26 and a force developing fuel flow section 28. A diaphragm 30 in section 26 connects on one side to the secondary venturi tube 18 through conduit 32 and receives air flow signals from said secondary venturi tube in the form of pressure changes. The other side of diaphragm 30 connects to the air conduit 12 through conduit 34 and receives air flow signals therefrom in the form of impact pressures. For any air flow through conduit 12 a pressure differential exists across diaphragm 30 which urges it to the right in Figure 1. A diagram 36 in section 28 divides this section into a fuel receiving chamber 38 and a metered fuel chamber 40. Primary and secondary fuel jets 42 and 44 allow the flow of fuel from chamber 38 from which said fuel flows to a fuel distribution chamber or rosette 46 for distribution to the separate cylinders of the engine through separate cylinder 7 48. Fuel feed conduit 20 receives fuel under constant pressure from fuel pump 52 immersed in tank 50 and discharges it into chamber 38.

:Tank 50 is vented to the atmosphere at 51 to bleed off excess fuel vapor therein. Return flow conduit 22 communicates with fuel source 50 and with chamber 38 across return flow orifice 54 and returns excess liquid fuel vapor purged from the feed fuel by the return flow current. Orifice 54 and metering member 56 connected to diaphragms 30, 36 and sealing diaphragm 58 comprise an adjustable return flow metering valve which regulates the flow of return fuel back to tank 50.

Throttles 60 and 62 pivotally mounted in air conduits 12 and 14 respectively are linked together by a lost motion arm 64 having a slot 66 in which a portion of link- The opposite end of arm 64 pivotally carries the linking projection 70. Primary throttle 60 is linked through arm 72 to the accelerator 74 and when said accelerator is depressed throttle 60 pivots clockwise. When throttle 60 is opened to a predetermined position arm 68 will abut the top of slot 66 and begin to open throttle 62. Since projection 78 is shorter than projection 68, secondary throttle 62 will be full open at the full open position of primary throttle 60. When the air flow to the engine is of relatively low .velocity, the pressure differential across the venturi 18 is not adequate to transmit sufficient signal to the adjustable fuel metering means 24 to thereby adjust the metering member 56 within the accuracy required for proper engine performance. Therefore, one-half of the air intake manifold, that is, passage 14, is closed by valve .62 so that all of the low velocity air flows through conduit 12 and venturi 18 to transmit suflicient signal to unit 24 to give the proper accuracy to the return fiow metering valve 56 at low engine speeds. As the total air consumption of the engine increases and the return flow metering signal transmitted by venturi 18 becomes too strong, throttle 62 in conduit 14 will be opened to allow .this additional air to be carried by conduit 14.

A jet valve means or member 76 is slidably mounted in section 28 and is linked through arms 78, 80, and 82 to secondary throttle 62 for movement away from the secondary jet 44 as throttle 62 is opened. The end 84 of valve member 76 is tapered at a selected angle to give a fuel flow through jet 44 which is linear with respect to the additional air flow through secondary conduit 14.

In describing the operation of the system of Figure 1 that the engine is idling and that throttles 60 and 62 and fuel metering member 56 are in their If such be the case, a substantially constant and major portion of the substantially constant quantity of fuel supplied by pump 52 to chamber 38 is returned to the tank 50 through return flow orifice 54 and the system is said to be in equilibrium. At such equilibrium the force exerted on diaphragm 36 by the pressure of the fuel in chamber 38 is equal to the 4 force exerted on diaphragm 30 by the pressure differential across diaphragm 30 plus the force exerted on diaphragm 36 by the pressure of the fuel in the metered fuel chamber 40. From the balancing of pressures it is seen that a pressure drop exists across primary fuel jet 42 which is equal to the pressure drop across diaphragm 30. Since the flow of fuel through jet 42 is proportional to the square root of the pressure drop thereacross it follows that said pressure drop must be proportional to the square of the desired fuel flow thereacross. The desired fuel flow normally is linear with respect to the air flow through conduit 12 and the pressure dilferential across diaphragm 36 must consequently be such as to exert a force tending to restrict the flow through orifice 54 an amount sufiicient to maintain a pressure drop across said jet 42 which is proportional to the square of the air flow. This is accomplished by the impact signal conduit 34 and by the secondary venturi tube 18 which reduces the pressure in chamber 18 as the square of the air flow through conduit 12. The primary venturi tube 16 is used to increase the air flow signal transmitted by tube 18 to diaphragm 30. As throttle 60 is opened additional air flow through venturi tube 18 will cause a pressure drop in conduit 32 which is again proportional to the square of the air flow.

The force on diagram 30 will again shift metering needle 56 to further restrict the flow of fuel back to the tank until the pressure drop across jet 42 is again equal to the pressure drop across venturi tube 18 and conduit 32. At this point the flow of fuel through jet 42 will be linear with respect to the air flow through tube 18 and conduit 12. As throttle 60 opens wide enough to open throttle 62 valve means 76 will open secondary jet 44 to allow an additional fuel flow to compensate for the additional air flow through secondary air intake conduit 14. The fuel flow through jet 44 varies directly as its area for a given pressure drop and the taper, therefore, of end 84 is such as to alter the area of jet 44 in direct proportion to the air flow through conduit 14.

The effectiveness of this system in reducing the amount of vapor present in the fuel delivered through jets 42 and 44 is obvious from a consideration of the return flow of fuel back to the tank, and the elimination of a fuel inlet metering valve. The flow of return fuel provides a medium for transferring or purging any fuel vapors in the feed fuel in chamber 38 or conduit 20 back to the tank. The elimination of an inlet metering valve at the entrance of fuel feed conduit 20 in 38 eliminates the formation of vapor in chamber 38 caused by the throttling effect of said valve. In the present invention the pressure drop and throttling effect is felt across return flow orifice 54 and any vapor formed thereby is transferred directly to the tank.

Referring to the variation of Figure 2 the metering system generally designated as 10 is essentially identical to that of Figure 1. In this variation, however, the secondary throttle 62 is not mechanically linked to the primary throttle 60 and to the secondary jet valve means 76 but is connected to said primary throttle and valve means indirectly through a fluid system. This fluid system comprises a main fluid or air flow signal transmitting conduit 76 which communicates with the primary venturi tube 16 of the primary manifold conduit and provides a fluid pressure passage to the pressure responsive throttle adjusting means 88 and the pressure responsive secondary jet valve adjusting means 90.

Throttle adjusting means 88 comprises a housing 92 containing flexible diaphragm 94 and providing pressure chamber 96 which connects to conduit 86 and receives the primary venturi signals. A vent 98 vents diaphragm 94 to the atmosphere on the side opposite chamber 96. A spring 100 prevents movement of diaphragm 94 and attached piston 102 linked to throttle 62 by arm 104 from opening throttle 62 until a predetermined air flow through primary conduit 12 occurs.

The secondary jet valve adjuster comprises a housin Figure 1 or may i ing 106 containing diaphragm 108 and providing pressure chamber 110 which connects to conduit 86 and venturi tube 16 to receive pressure signals therefrom. The opposite side of diaphragm 108 is Vented to the atmosphere through vent 112. Spring 114 prevents valve means 76 from opening secondary jet 44 until a predetermined air flow through conduit 12 occurs.

The operation of the structure of Figure 2 is substantially that of Figure 1 except that the operations of the secondary throttle adjusting means 88 and the secondary jet valve adjuster 90 are automatic in response to a predetermined air flow through the primary air intake conduit 12 which air flow is sufficient to transmit a pressure signal strong enough to overcome the force of springs 100 and 114. When this predetermined air flow occurs in conduit 12, assuming the primary and secondary fuel jets and the primary and secondary air intake conduits to be of equal capacity, secondary throttle 62 and secondary fuel jet 44 will begin to open an equal amount percentage wise and when secondary throttle 62 is wide open secondary jet 44 is wide open and both air flow to the engine and fuel flow to the engine is doubled.

Referring to Figure 3 an additional air pressure responsive means 116 and air flow metering means 118 and 120 are provided on metering means 24 and air conduit 14 respectively and are connected through conduit 122. Diaphragm 124 in means 116 communicates on one side with venturi tube 120 and on the other side with air conduit 14 through conduit 126 and is connected to needle 56 in an equivalent manner to diaphragm 30. Diaphragm 124 is larger than diaphragm 30 so as to increase the pressure drop across jet 42 as the square of the additional air flow in conduit 14. Assuming conduits 12 and 14 to be of the same size, diaphragm 124 would necessarily have an effective area three times as large as that of diaphragm 30 to establish the aforementioned pressure drop. Since the additional fuel flow is provided by an additional force on needle 56, secondary jet 44 is eliminated in the variation of Figure 3. The linkage between the throttles of Figure 3 is the same as be a fluid linkage such as 86, 88, 102, and 104 shown in Figure 2.

In all three figures the sizes of the venturi tube, diaphragms, and fuel jets are particularly determined to give the fuel flow required by the engine. The most practical way of adjusting the fuel flow for a particular application of the system is to vary the size of the fuel jets after the venturi tubes and diaphragms have been selected.

I claim:

1. A fuel metering system for an internal combustion engine comprising a primary air intake conduit, a venturi tube located in said primary conduit, a fuel feed conduit connected to said engine and a fuel supply, said fuel supply adapted to feed fuel to said fuel feed conduit under substantially constant pressure and in an amount in excess of the maximum amount required by the engine, a return flow conduit connecting said fuel feed conduit to said fuel supply, pressure responsive adjustable fuel metering means associated With said return flow conduit, said means being operatively connected to said venturi tube and adapted to regulate the flow of fuel through said return flow conduit according to the air flow through said venturi tube, a secondary air intake conduit having throttle means therein for regulating the flow of air therethrough, and adjustable fuel jet means in said fuel feed conduit connected to said throttle means and responsive to movement thereof to further adjust the flow of fuel to said engine in direct proportion to the air flow in said secondary air intake conduit.

2. A fuel metering system for an internal combustion engine comprising a primary air intake conduit, air metering means located in said primary conduit, a fuel feed conduit connected to said engine and a fuel supply, said fuel supply adapted to feed fuel to said fuel feed conduit under substantially constant pressure and in an amount in excess of the maximum amount required by the engine, a return flow conduit connecting said fuel feed conduit to said fuel supply, pressure responsive adjustable fuel metering means associated with said return flow conduit, said means being operatively connected to said air metering means and adapted to regulate the flow of fuel through said return flow conduit according to the air flow through said air metering means, a secondary air intake conduit having throttle means therein for regulating the flow of air therethrough, and adjustable fuel jet means in said fuel feed conduit connected to said throttle means and responsive to movement thereof to further adjust the flow of fuel to said engine in direct proportion to the air flow in saidsecondary air intake conduit.

'3. A fuel metering unit for an internal combustion engine comprising a primary and a secondary air conduit for supplying air to said engine, a constant delivery fuel supply, a fuel feed conduit connecting said fuel supply to said engine, a primary and a secondary fuel jet in said fuel feed conduit, a return flow conduit connected to said fuel feed conduit at a point intermediate said fuel supply and said jets and communicating with said fuel supply, a primary and a secondary air throttle in said primary and secondary air conduits respectively, air flow and fuel flow responsive return flow metering means operatively associated with said return flow conduit, said metering means being, operatively connected to said primary air conduit and said fuel feed conduit and adapted to regulate the flow of return fuel according to air flow through said primary air conduit, and jet valve means connected to said secondary air throttle and operative to open said secondary fuel jet, in response to opening of said throttle, said secondary throttle being operatively linked to said primary throttle to open at a predetermined position of said primary throttle.

4. A fuel metering unit for an internal combustion engine comprising a primary and a secondary air conduit for supplying air to said engine, a constant delivery fuel supply, a fuel feed conduit connecting said fuel supply to said engine, a primary and a secondary fuel jet in said fuel feed conduit, a return flow conduit connected to said fuel feed conduit at a point intermediate said fuel supply and said jets and communicating with said fuel supply, a primary and a secondary air throttle in said primary and secondary air conduits respectively, a primary and a secondary venturi tube in said primary air conduit, air flow and fuel flow responsive return flow metering means connected to said secondary venturi tube and said return flow conduit and adapted to regulate the flow of return fuel according to air flow through said primary air conduit, and jet valve means connected to said secondary air throttle and operative to open said secondary fuel jet in response to movement of said throttle to an open position, said secondary throttle being operatively linked to said primary throttle to open at a predetermined position of said primary throttle.

5. A fuel metering unit for an internal combustion engine comprising a primary and a secondary air conduit for supplying air to said engine, a constant delivery fuel supply, a fuel feed conduit connecting said fuel supply to said engine, a primary and a secondary fuel jet in said fuel feed conduit, a return flow conduit connected to said fuel feed conduit at a point intermediate said fuel supply and said jets and communicating with said fuel supply, a primary and a secondary air throttle in said primary and secondary air conduits respectively, a primary and a secondary venturi tube in said primary air conduit, air flow and fuel flow responsive return flow metering means connected to said secondary venturi tube and said fuel feed conduit and adapted to regulate the flow of return fuel according to air flow through said secondary venturi tube, secondary jet valve means operatively associated with said secondary fuel jet, pressure responsive jet valve adjusting means connected to said jet valve means and communicating with said primary venturi tube, and pressure responsive throttle adjusting means connected to said secondary throttle and communicating with said primary venturi tube, said jet valve adjusting means and said throttle adjusting means being operative to open said secondary jet and said secondary throttle respectively at a predetermined air flO'W past said primary venturi tube.

6. A fuel metering unit for an internal combustion engine comprising a primary and a secondary air conduit for supplying air to said engine, a constant delivery fuel supply, a fuel feed conduit connecting said fuel supply to said engine, a primary and a secondary fuel jet in said fuel feed conduit, a return flow conduit connected to said fuel feed conduit at a point intermediate said fuel supply and said jets and communicating with said fuel supply, a primary and a secondary air throttle in said primary and secondary air conduits respectively, air flow metering means in said primary air conduit, air flow and fuel flow responsive return flow metering means connected to said secondary venturi tube and said fuel feed conduit and adapted to regulate the flow of return fuel according to air flow through said air flow metering means, secondary jet valve means operatively associated with said secondary fuel jet, pressure responsive jet valve adjusting means connected to said jet valve means and communicating with said air flow metering means, and pressure responsive throttle adjusting means connected to said secondary throttle and communicating with said air flow metering means, said jet valve adjusting means and said throttle adjusting means being operative to open said secondary jet and said secondary throttle respectively at a predetermined air flow past an air flow metering means.

7. A fuel metering system for an internal combustion engine comprising primary and secondary air intake conduits, air flow metering means in each said air conduit, fuel conduit means communicating with a fuel supply and said engine, and pressure responsive adjustable fuel metering means in said fuel conduit means adjustable to vary the flow of fuel therethrough, said fuel metering means being operatively connected to each said air flow metering means in each said air conduit and adjustable thereby in response to air flow through each said air conduit, said metering means in said secondary air intake conduit becoming active to adjust said fuel metering means upon a predetermined air flow in said primary air intake conduit.

8. A mass flow responsive fuel control system for an internal combustion engine comprising primary and secondary air intake conduits adapted to be operatively connected to said engine, air flow metering means in each of said conduits, constant delivery fuel feed means for sup- 8 plying fuel to said engine, return flow means connected to said feed means to purge fuel vapors therefrom, pressure responsive adjustable fuel metering means in said return flow means for regulating the flow therethrough, said fuel metering means being operatively connected to each said air flow metering means and adjustable thereby to regulate the flow of fuel to the engine in linear proportion to the air flow thereto.

9. A mass flow responsive fuel control system for an internal combustion engine comprising primary and secondary air intake conduits adapted to be operatively connected to said engine, air flow metering means in each said conduit, constant delivery fuel feed means for supplying fuel to said engine, return flow means connected to said fuel feed means to purge fuel vapors therefrom, pressure responsive adjustable fuel metering means in said return flow means for regulating the flow therethrough, said fuel metering means comprising a shiftable member connected to two air pressure responsive diaphragm devices, said diaphragm devices being connected to said air flow metering means in said air intake conduits and responsive to air flow through said air intake conduits to adjust said fuel metering means to regulate the flow of fuel to the engine in linear proportion to the air flow thereto.

10. A fuel metering unit for an internal combustion engine comprising-a primary and a secondary air conduit for supplying air to said engine, a venturi tube in each said air conduit for measuring air flow therethrough, a constant delivery fuel supply, a fuel feed conduit connecting said fuel supply to said engine, a primary fuel jet in said fuel feed conduit, a return flow conduit connected to said fuel feed conduit at a point intermediate said fuel supply and said jet and communicating with said fuel supply, adjustable valve means in said return flow conduit for regulating the fuel flow therethrough, air pressure responsive means connected to said adjustable valve means for adjusting same, said air pressure responsive means being connected to said venturi tube in each said air conduit for receiving air flow signals therefrom and being responsive to said signals to adjust said valve means according to air flow through said air conduits.

References Cited in the file of this patent UNITED STATES PATENTS 2,487,774 Schipper Nov. 8, 1949 2,803,233 Demtchenko Aug. 20, 1957 2,843,096 Dolza et al. July 15, 1958 2,882,880 Reggio Apr. 21, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 295L467 October 25 1960 Thomas M Ball It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

column 7 line 32, for "an" read said Column 2 line 5 for "ronduit read conduit column 8, line 2 after "said insert fuel e Signed and sealed this 25th day of April 1961.

(SEAL) Attest:

ERNEST we SWIDER Attesting Ofiicer DAVID L LADD Commissioner of Patents Disclaimer Thomas M. Ball, Bloomfield Hills, Mich. FUEL METERING SYSTEM. Patent dated Oct. 25, 1960. Disclaimer filed Nov. 26, 1962, by the inventor and the: assignee, Uiwyslw' Corporation. Hereby enter this disclaimer to claims 7, 8, 9 and 10 of said patent.

[Ofiio-ial Gazette J emuwy 1, 1.963.] 

